Ignition System - C3I: Description

The Computer Controlled Coil Ignition (C(3)I) system, used on 3.3L and 3.8L engines, eliminates the need for a mechanical distributor. The C(3)I system consists of a coil pack, ignition module, camshaft (3.8L) and/or combination sensor, wiring harness, and the Electronic Spark Timing (EST) portion of the Electronic Control Module (ECM). Ignition timing is controlled by the ECM based upon inputs signals from the, camshaft position sensor (3.8L), engine RPM reference line, coolant temperature sensor, manifold air temperature sensor, throttle position sensor, knock sensor, vehicle speed sensor, gear position switch, and the mass airflow sensor.

In the C(3)I system, each cylinder is paired with the cylinder that is opposite it in the firing order. Cylinders No. 1-4, 5-2, and 3-6 are paired. Spark occurs simultaneously in the cylinder coming up on the compression stroke and in the cylinder coming up on the exhaust stroke. The cylinder on the exhaust stroke requires less voltage for the spark plug to fire. This leaves the bulk of the available voltage to fire the spark plug for the cylinder on the compression stroke. The process is repeated when the cylinders reverse roles. Each cylinder pair is fired by its own ignition coil.